Method and foreign agent group for registering to a home agent of a mobile node

ABSTRACT

The present invention provides an improved solution of registering with a Home Agent HA of a Mobile Node MN, comprising: grouping at lest two Foreign Agents FAs to form a Foreign Agent Group FAG to enable FA members of the FAG to share information of the MN roaming into a FAG coverage area; when any FA member of the FAG receives a registration request for registering a care-of address with the HA sent by the MN, determining whether the MN enters the FAG coverage area for the first time based on the shared MN information; and if the MN enters the FAG coverage area for the first time, the FA forwards the received registration request to the HA; otherwise, the FA directly sends a registration response to the MN. The solution of the present invention greatly reduces registration messages from the MN to the HA, thereby reducing signaling delay produced when the MN moves in the FN. Also, both the MN and the HA in the prior art can be merged into the solution, thereby achieving seamless integration with IPv4, preferably with Mobile IPv4 scheme.

FIELD OF THE INVENTION

The invention relates to the field of IPv4, and particularly toachieving seamless network-layer handover in the IPv4.

BACKGROUND OF THE INVENTION

With the popularity of the Internet and development of mobilecommunications, users increasingly need to be able to access theInternet at anytime and anywhere, which causes provision of mobileInternet access to become one of hotspots of Internet technologyresearch. Mobile IP is a solution supporting movement of a node providedon the basis of original IP protocol, which enables people to be able toconnect to the Internet at anytime via terminals like notebook computer,PDA (personal digital assistant) or the like, no matter where he/she is,for example at home, on a train or airplane. It is important that as themovement of the location of a user terminal, the user terminal's IPaddress remains unchanged, regardless of where the mobile device isactually located. Thus enable other devices to be able to access theuser terminal with this IP address, consequently maintaining thecontinuity of communication during the movement. Therefore, the MobileIP achieves free access to the Internet by users.

As shown in FIG. 1, the IPv4-based Mobile IP defines three functionalentities: Mobile Node MN, Home Agent HA and Foreign Agent FA. The MobileNode MN is a mobile terminal which may change its network attachmentpoint by moving, such as notebook computer. PDA, cell phone, etc. The MNhas a Home Address HoA in its home network, and the Home Address HoAwhich is fixed as other addresses of fixed hosts is provided by the HomeNetwork HN. For a Mobile Node which has moved, regardless of where itscurrent attachment point is, the Mobile Node still seems to be connectedto the Home Network from the perspective of other devices in thenetwork. The Home Agent is a node located within the Home Network of theMobile Node, typically, it is a router. When the Mobile Node leaves theHome Network and enters into a Foreign Network, it registers itsobtained care-of address with the Home Agent. The Home Agent keeps thecurrent location information of the Mobile Node, and when interceptingdata packets destined to the home address of the Mobile Node, tunnelsthe data packets to the Mobile Node. The Foreign Agent FA is a host in aForeign Network when the Mobile Node moves to the Foreign Network FN,usually, it is a router which may provide routing services for MobileNodes and may also release the tunnel encapsulation for the tunneledpackets from the HA of the MN and send the de-encapsulated data packetsto MN. Both the HA and FA may periodically send an agent advertisemessage from which MNs can determine whether they are located in theHome Network HN or the Foreign Network FN. When a Mobile Node is in FN,a care-of address CoA can be obtained from the received foreign agentadvertise message, such as Foreign Agent care-of address. Also, acare-of address can also be allocated by a Foreign Network, such asCo-located care-of address CoCoA. Wherein, the CoCoA is a separate IPaddress allocated by the FN to the MN, and the Mobile Node may receivetunneled packets with encapsulation. The Mobile Node using the FACoAthen receives de-encapsulated packets forwarded by the FA.

In the IPv4 environment, each time the MN moves from one of foreignagents to another, it registers the care-of address to its Home Agent.Therefore, in order to keep the continuity of a session, handover delayof the network-layer handover and packet loss need to be reduced to theminimum. The existing technology acquires seamless network-layerhandover mainly by two manners. The first one is to directly reduce thepossible delay of the procedures needed in handover, e.g. for reducingthe delay of some procedures in handover, overlapping several proceduresin the handover to reduce the overall handover delays (i.e.,Registration in advance). However, it is difficult to get a seamlessnetwork-layer handover merely by the first manner. For example, if thedistance between the Foreign Network and the Home Network of the MobileNode is too large, the signaling delay for a registration may be verylong.

As shown in FIG. 2, the second manner is Regional Registration Solution.In this solution, in order to reduce registration, a new network elementnamed Gateway Foreign Agent GFA is added in the FN. The Gateway ForeignAgent as the central node is responsible for the maintaining anddistributing a list of visitors, and forwarding data. In control plane,all the registration requests transmitted from MN to Home Agent HA areforwarded by the current FA to the GFA, and the GFA further determineswhether it is necessary to forward the registration requests to HA.Moreover, the Gateway Foreign Agent collects and maintains all thevisitor information and distributes it to other foreign agents in thevisited domain. U.S. Patent US7069338B2 details the RegionalRegistration Solution, and details for the solution are not describedhere any more. Thus, the topology between the Gateway Foreign Agent andassociated all foreign agents of regional registration located withinthe same visited domain is fixed, which lacks flexibility in deployment.Moreover, the solution requires not only setting an additional GatewayForeign Agent in the network, but also the regional-registration-relatedfunction being supported in the Home Agent HA, Foreign Agent FA as wellas Mobile Node MN, which will greatly increase implementation cost,prone to be rejected by most vendors and operators. Also, the drawbacksdifficult to overcome by the solution are: for existing MNs, they cannot benefit from the solution because they can not support thecorresponding regional registration function; for existent HAS and FAs,they can not be integrated into this solution, because they can notsupport the corresponding function, too.

As it can be seen, an improved solution is still needed in order toachieve the minimization of the number of signaling messages arriving atthe Home Network, thus reducing the signaling delay produced when the MNis moving in the FN.

SUMMARY OF THE INVENTION

To address the above drawbacks in prior art, the present inventionproposes an improved method for registering with the HA of the roamingMN in the IPv4, which greatly reduces the number of signaling messagesto the Home Network.

The present invention provides a method for registering with a HomeAgent HA of a roaming Mobile Node MN in IPv4, the IPv4 comprising atleast one Mobile Node MN and a Home Agent HA and further comprising atleast two Foreign Agents FAs, the method comprising the steps of:

A. selecting at least two FAs from the Foreign Agents FAs to form aForeign Agent Group FAG;

B. FA members of the FAG sharing information of the MN roaming into aFAG coverage area;

C. when any one FA member of the FAG receives a registration request forregistering a care-of address with the HA sent by the MN, determiningwhether the MN enters into the FAG coverage area for the first timebased on the shared MN information;

D. if the MN enters into the FAG coverage area for the first time, theFA forwards the received registration request to the HA; otherwise,directly sends a registration response to the MN.

Preferably, the FAs of the FAG may be link neighboring or subnetneighboring or network coverage area neighboring FAs. Preferably, theFAs of the FAG maintain a Visitor Information Table VIT and/or anOver-group Visitor Information Table OVIT in order to maintain the MN'sinformation.

In the step C, when the MN uses a Foreign Agent Care-of Address FACoA asthe care-of address, the FACoA is an address of the FA which is servingthe MN currently, or an Anycast Address AA configured to the FAG; andwhen the MN uses a Co-located Care-of Address CoCoA as the care-ofaddress, the CoCoA within the FAG coverage area is configured for theMN. Preferably, the FA determines whether the MN enters into the FAGcoverage area for the first time based on the MN's Home Address HoA orCo-located Care-of Address CoCoA.

In the step D, the FA updates the MN information, and marks itself asthe FA which is serving the MN currently.

In the step A, a part of the FA members of the FAG is selected as aForwarding Cooperative FA to be responsible for distributing andmaintaining the shared MN information, or a dedicated ForwardingCooperative FA is set in the FAG for distributing and maintaining theshared MN information and forwarding data packets.

Preferably, the dedicated Forwarding Cooperative FA is arranged at anode within the FAG coverage area through which the amount of datapackets passing is large, or at a main or hub path from the HA to the FAmember of the FAG.

The invention also provides a Foreign Agent Group FAG for registeringwith a Home Agent HA of a roaming Mobile Node MN in IPv4, the IPv4comprising at least one Mobile Node MN and a Home Agent HA and furthercomprising at least two Foreign Agents FAs, characterized in that:

at least two said FAs are grouped as a FAG, FA members of the FAGsharing information of the MN roaming into a FAG coverage area;

the FA of the FAG comprising:

shared information acquisition means for acquiring shared informationfrom other FAs of the FAG;

management means for determining whether the MN enters into the FAGcoverage area for the first time based on the shared information, when aregistration request for the MN registering a care-of address with theHA is received; and

registration processing means for forwarding the registration request tothe HA, if the management means determines that the MN enters into theFAG coverage area for the first time; otherwise, sending a registrationresponse directly to the MN.

Preferably, the management means of the FA maintains a VisitorInformation Table VIT and/or an Over-group Visitor Information TableOVIT in order to maintain the MN's information. Preferably, when themanagement means determines that it is not the first time for the MN toenter into the FAG coverage area, it marks itself as the FA which isserving the MN currently.

The management means of the FA member sets a care-of address in amobility agent advertisement extension in an agent advertisement as anAnycast Address AA or the address of the FA, or configures the CoCoAwithin the FAG coverage area as the care-of address for the MN.

Preferably, a part of the FAs of the FAG are set as ForwardingCooperative FAs on which the management means is responsible fordistributing and maintaining the shared MN information, or a dedicatedForwarding Cooperative FA is arranged in the FAG for distributing andmaintaining the shared MN information and forwarding data packets.

The invention also provides a Foreign Agent FA for registering with aHome Agent HA of a Mobile Node MN in IPv4, the IPv4 comprising at leastone Mobile Node MN and a Home Agent HA, and further comprising at leasttwo FAs for sharing information of the MN roaming into its coverageareas with other FAs, for determining whether the MN enters into the FAGcoverage areas for the first time based on the shared information, whenreceiving a registration request for the MN registering a care-ofaddress with the HA, and for forwarding the registration request to theHA, if the MN enters into the FAG coverage areas for the first time,otherwise sending a registration response directly to the MN.

The present invention also provides a computer program for handlingregistration with a Home Agent HA of a Mobile Node MN in IPv4, the IPv4comprising at least one Mobile Node MN and a Home Agent HA and furthercomprising at least two Foreign Agents FAs, the computer programcomprising instructions to perform:

grouping at least two FAs as a Foreign Agent Group FAG;

FA members of the FAG sharing information of the MN roaming into a FAGcoverage area;

when any one FA member of the FAG receives a registration request forregistering a care-of address with the HA sent by the MN, determiningwhether the MN enters into the FAG coverage area for the first timebased on the shared MN information;

if the MN enters into the FAG coverage area for the first time, the FAforwards the received registration request to the HA; otherwise, the FAsends a registration response directly to the MN.

The invention also provides a storage medium on which computer-readableinstructions for performing the method, the Foreign Agent Group FAG andthe Foreign Agent FA according to the invention are stored thereon.

The invention also provides a computer system that includes a processorwith computer-readable instructions for performing the method, theForeign Agent Group FAG and the Foreign Agent FA according to theinvention thereon.

The improved solution provided by the present invention greatly reducesregistration messages from the roaming MN to the HA, thereby reduces thesignaling delay produced when the MN moving in the FN. Compared with theregional registration solution, the present invention provides a moresimple and flexible solution to avoid setting new elements in thenetwork and attaching additional function supported in MN, HA, whichgreatly reduces deployment costs. Moreover, for FAs of the FAG, thedistributing of the shared MN information (e.g. OVIT) can be designed tobe either centralized, i.e. one or several selected FA members maintain,collect and distribute the shared information and updates information toother FA members, or dispersed, i.e. each FA maintains the sharedinformation and once information is updated, any FA member maydistribute it to other FA members. As a result, the solution provides amore flexible deployment, which can adapt itself to more networks.According to the “FAG” solution of the invention, for the MN and HA,they do not feel the existence of the FAG as well as changes among FAmembers of the FAG. That is, only the FAs of the FAG will know thedifference between the solution and the prior art. Thus, both MN and HAin the prior art are enabled to join into the solution and to benefitfrom the solution, achieving seamless integration with the existingIPv4, especially the Mobile IPv4.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of network topology structure when a Mobile Nodemoves across a Foreign Network in an IPv4 environment;

FIG. 2 shows an example of network topology structure of a regionalregistration solution;

FIG. 3 shows an example of network topology structure when a Mobile Nodemoves across a Foreign Network in an IPv4 environment arranged with FAGaccording to the invention;

FIG. 4 shows an example of structure of a FA in the FAG;

FIG. 5 shows a flowchart of the MN using FACoA as a care-of address toregister with HA according to the invention;

FIG. 6 shows a flowchart of the HA forwarding the received data packetsdestined to the MN's HoA with respect to the MN which uses FACoA as acare-of address according to the invention;

FIG. 7 shows a flowchart of the MN which uses FACoA as a care-of addressaccording to the invention sending data packets to a Communication NodeCN; and

FIG. 8 shows another example of network topology structure when a MobileNode moves across a Foreign Network in an IPv4 environment arranged withFAG according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The basic idea of the present invention is to select some FAs,preferably, some neighboring FAs, such as link neighboring, subnetneighboring, network coverage area neighboring or FAs neighboring inother manners, to form a cooperative group named Foreign Agent Group.The network served by the FAG is named with Visited Domain VD. Inaddition to maintaining, like FAs in an IPv4 environment, information ofMNs moving into the areas thereof, for all the FA members belonging tothis group, each of the FA members can share information of MNs roaminginto respective serving areas among them, especially the registrationinformation, thereby can share information of any MN moving into the VD.Through the sharing of MN information, only when a MN moves into the VDarea for the first time, a FA of the FAG registers the MN's care-ofaddress with the MN's HA, and thereinafter, when the MN movesacross/within FNs within the VD, registration with the HA is no longerneeded to be performed. That is, for the MN roaming into the VD,registration with the HA is needed only when it first enters the VD, andregistrations with the HA are no longer needed thereinafter as long asMN still moves within the VD. Thus, the FAG of the present inventionacts as one FA for the HA and MN. Therefore, the improved solution ofthe present invention significantly reduces registration proceduresbetween the roaming MN and the HA, thereby reducing signaling messagesto the HA, and further reducing signaling delay when the MN moves in theVD.

FIG. 3 shows an example of a MN moving in a VD served by a FAG in anIPv4 environment. Typically, the IPv4 environment comprising three typesof functional entities: Mobile Node MN, Foreign Agent FA and Home AgentHA, wherein meanings and functions of the MN and HA are similar to thosein the prior art. In the example shown in FIG. 3, the MN has a HomeAddress HoA in the HN, while router 1 is the MN's HA. FA1, FA2, FA3 arethe respective FAs in foreign networks FN1, FN2, FN3 whose networkcoverage areas are neighboring. In this example, FA1, FA2 and FA3 areconstituted as a FAG, so that the three become cooperative FAs, andareas served by FN1, FN2 and FN3 form a VD. For a FA member of the FAG,it should know addresses of other FA members within the group, andshould also know the ID of the FAG which it belongs to, thus to identifydifferent FAGs, which can be achieved by manual or automaticconfiguration. Preferably, for the MN using FACoA as its care-ofaddress, an Anycast Address AA can be configured for the FAG as the MN'scare-of address, while the AA at this time may also be the ID of theFAG. In addition, a FA can be set and added into multiple different FAGsconcurrently, then the FA at this time recognizes the FAGs which itbelongs to by identification, wherein different IDs identify differentgroups, which can be achieved by manual or automatic configuration.Preferably, different FAGs can be set flexibly based on factors such asneighboring situations among FAs in an application environment as wellas moving frequency of the MN or the like.

FIG. 4 shows an example of structure of the abovementioned FA1-3. Here,in addition to functions such as mobility agent advertisement or thelike in the prior art, the FA further comprises shared informationacquisition means for acquiring shareable information about the MN fromother FA members of the FAG. Management means is used for maintainingOver-group Visitor Information Table OVIT and Visitor Information TableVIT. VIT is created by the registration process of IPv4 protocol at eachFA member of the FAG. Such list is a set of “visitor information entry”.Necessary columns included in the Visitor Information Entry are: MN'sHome Address HoA, HA Address, the address of current FA namely CFA(Current Foreign Agent), and the Lifetime of the current registration,wherein “CFA” indicates which FA is providing services to the MNcurrently. In the situation where the MN uses CoCoA as its care-ofaddress, the column “MN's CoCoA” should also be included in the table.VITs of all the FA members of the FAG can be combined into an OVIT,which is shared by all the FA members, here shared by FA1-3. Forachieving sharing of the visitor information, management means in a FAmember regularly (e.g., periodically) or triggered by request from aspecific FA member, or triggered by changes in its VIT, managesdistribution of update information in its VIT to other FA members of theFAG. The distribution may be delivered by IP unicast UDP, or othermanners capable of delivering update information to other FA members,such as delivery manners of TCP, multicast, or the like, can also beused. Each of the other FA members receiving the advertisement updates(including adding, deleting, changing or the like operations) its VITand OVIT. When the FA receives a registration request from the MN, themanagement means is responsible for determining whether it is the firsttime for the MN to enter into the VD. In addition, registrationprocessing means in the FA is used for processing registration-relatedtransactions, such as sending a registration request to the MN's HA,sending a registration response to the MN and so on.

The structure of a FA shown in FIG. 4 is just an example Those skilledin the art should understand that the manage means in the above examplemay also be divided according to its corresponding functions intomaintenance means (for maintaining shared information, such as OVIT),determination means (for determining whether it is the first time forthe MN to enter into the VD), etc. Similarly, the management means andregistration processing means in the above example can also beintegrated together. In summary, the specific structure of the FA is notunique, and not limited to the structure in the example above. Under thepremise of being able to share the information of the MN entering intothe VD and to determine whether the MN is entering into the VD for thefirst time, its specific structure can be set flexibly, means andmodules therein can be integrated or divided, or means and modules forimplementing other functions can also be added.

Optionally, FA members of the FAG do not have to be neighboring. Forexample, if it is known that some MNs will move to some specific FNareas, related FAs can be constituted directly as a FAG, and it isobvious that these FAs do not have to be neighboring.

It should be noted that in the above example, each FA member maintainstwo tables VIT and OVIT, when VIT maintained by some FA is updated, onlythe updated information is sent to other FA members, so that the FA'sown services can be separated from the FAG's information, which alsorealizes full utilization of network resources and is a preferredsolution. However, those skilled in the art may understand that inspecific applications, based on different carrying capability of each FAmember and different usage of resources, each FA member may also beallowed to maintain only one of the two tables, while the solution ofthe invention can be realized as long as the sharing of MN informationwithin the FAG can be achieved. Of course, if necessary, a FA member mayalso send other information in its maintained VIT or OVIT to other FAmembers, not just the updated information.

Optionally, depending on specific applications, a part of the FA membersof the FAG are arranged to maintain VIT or OVIT, while other FA memberstemporarily acquire shared MN information when necessary. Such situationmay be, for example, a situation in which fewer FA members of the FAG orfewer services within areas covered by the FAs, or a situation whereshared areas are divided logically for FA members of the FAG having moremembers, within each of the shared area, one FA may be selected tomaintain shared information while other FAs within this area temporarilyacquire desired information from the FA maintaining shared information.In short, those skilled in the art can understand that manners ofsharing the MN's information among FA members of the FAG are various andcan be selected flexibly based on specific application environments.

In addition, for the MN using FACoA as its care-of address, each FAmember of the FAG sets the Anycast Address AA as a preferred care-ofaddress in a mobility agent advertisement extension in an agentadvertisement, so that the MN obtains the AA and adds it into aRegistration Request RRQ. FA members of the FAG advertise routinginformation of the FAG's AA to a NSP (Network Service Provider) network,or advertise to an IP core network, so that data packets with theAnycast Address AA as their destination can arrive at FA members of thegroup.

For a MN roaming outside the HN and moving across the VD, both FACoA andCoCoA can be used as the care-of address. With respect to the two casesabove, the process of the MN registering with the HA and the process ofdata packet forwarding are described below respectively.

1. Using Foreign Agent Care-of Address FACoA as care-of address

1.1 Registration process

FIG. 5 shows the registration process when the MN uses the FACoA as itscare-of address. In this example, as mentioned above, all FA members ofthe FAG advertise the AA as the FACoA, so that the “CoA” field in theregistration request is set as the AA. Specifically, when the MN movesacross a Foreign Network FN in the VD, it receives the mobility agentadvertisement and does mobility detection to acquire a care-of address,step 501. As the mobility detection is usually based on network prefixchanging detection or lifetime of “Router Advertisement” received by theMN, setting of the FACoA does not impact the MN's mobility detection.For the MN, the AA has no difference with respect to the FACoA in thereceived mobility agent advertisement in the general IPv4. When the MNfinds that it has moved outside of the HN and to the FN, for example, inFIG. 3, the MN moves from position 1 in the HN to position 2 within theFN1 in the VD, it sends a registration request RRQ to the HA, in orderto register the acquired care-of address, step 502. As mentionedpreviously, the MN initiates a Registration process as specified inIPv4, preferably in Mobile IPv4, using the FAG'S Anycast Address AA asthe care-of address. When the CFA in the VD, here FA1, receives the MN'sRRQ, it looks up OVIT using the MN's Home Address HoA as a keyword todetermine whether there exists a matched visitor list entry, step 503.If there is no matched entry, that means the MN enters into the VD forthe first time (moves from some network not included in the visiteddomain into the current network). In this case, the FA1 needs to forwardthe RRQ from the MN to the MN's HA and register the MN's care-of addressAA, step 504. The FA1 creates a visitor list entry in its maintained VITand OVIT for MN, and then distributes this entry to other FA memberswithin its group. After receiving the RRQ, the HA binds the MN's HoAwith the received AA, and then sends a Registration Response RRP to theFA1, step 505. FA1 forwards the RRP from the HA to the MN, to completethe registration process defined in IPv4, step 506. With the aboveoperations, the MN's visitor list entry is added into the CFA's VIT andOVIT, and the CFA distributes the update of the OVIT to other members ofthe FAG and other members update their OVIT accordingly. If there is onematched entry, it means that the MN moves from some network included inthe visited domain into the current network, for example, the MN movesfrom position 2 in FIG. 3 to position 3. In this case, the CFA (hereFA2) only needs to update the entry, not to forward the RRQ from the MNto the HA followed by further initiation of the registration of care-ofaddress, but directly sends the RRP to the MN, step 507. Here, updatemeans FA2 replaces the old CFA address (FA1) with its address andupdates the old lifetime, then distributes update information to othermembers of the FA group.

1.2 Forwarding Process

FIGS. 6 and 7 show respectively transmission processes of the IP packetswhen the MN moves out of the HN and travels through networks in the VD.Here, the description is given by way of example where the MN moves fromthe HN to the FN2 area in the VD in the network environment as shown inFIG. 3.

As shown in FIG. 6, for a packet from a communication node CN anddestined to HoA of the MN away from the HN, the MN's HA intercepts thepacket, step 601. The HA forwards the packet as specified in IPv4,preferably in Mobile IPv4: the packet will be tunneled to the AAindicated in the binding information maintained by the HA, step 602.Because FA members of the FAG have advertised the AA to the NSP Network,the tunneled packet sent by the HA will be routed to the FA nearest tothe HA (being nearest usually refers to policy-based,routing-hop-number-based, delay-based, bandwidth-based, etc.). Thenearest FA in this example is the FA1 in the FN1, After receiving thepacket, FA1 will check the validity of the tunneled packet as specifiedin IPv4 and then look up OVIT using the inner IP destination address ofthe tunneled packet, i.e. the MN's HoA, as a keyword, to get known theMN's CFA which is serving the MN currently, step 603. If there is amatched entry in OVIT, the packet is forwarded to the CFA (FA2 in thisexample) by IP tunneling or by inserting IP routing option, step 604.After the CFA receives the packet, it checks the validity of the packetand looks up its OVIT using the inner IP destination address of thepacket, i.e. the MN's HoA, as a keyword, step 605. If there is a matchedentry, the inner packet will be forwarded to the MN, step 606. If thereis no matched entry in the CFA's OVIT, the packet is discarded silently,step 607.

As shown in FIG. 7, for a packet from a MN away from HN to acommunication node, the packet is forwarded directly to its first hoprouter CFA (FA2 in this example), step 701. The CFA checks whether theMN is a registered visitor: looks up OVIT using the source IP address ofthe data packet, i.e., the MN's HoA, as a keyword, step 702. If there isa matched entry in the OVIT of the CFA (here FA2), it means that thepacket source is a registered visitor and the CFA forwards the packet tothe communication node by normal forwarding mechanism, step 703.Otherwise, if there exists no matched entry in the CFA's OVIT, thepacket is not from a registered visitor and the packet is discardedsilently, step 704.

The registration of care-of address with the HA process as well as theprocess of data forwarding between the MN and the CN when the roaming MNuses FACoA as its care-of address are described above. As a preferredsolution, the FAG in the example is configured with the Anycast AddressAA and takes it as the MN's care-of address. However, those skilled inthe art should understand that according to the idea of the invention,as long as FA members of the FAG can share information of the MN roaminginto the VD, the solution of the present invention can be realized, andit is not necessary to configure the Anycast Address AA for the FAG.

For example, according to the principle of the invention, for FAs in theexisting IPv4 network environment, two or more FAs, which are linkneighboring, subnet neighboring, network coverage area neighboring orneighboring in other forms, are selected to form the FAG. Here stilltaking FIG. 3 as an example, the FA1, FA2, FA3 are grouped to form theFAG, and the sharing of information of the MN roaming to the servingarea thereof among every FA of the FAG is achieved by some mechanism,such as by forwarding, when each FA updates the table which itmaintains, update information timely to other FA members in unicast ormulticast or the like manners, or by periodical forwarding. When the MNmoves out of the HN and moves across the VD to the FN1, the MN findsthat it has moved outside of the HN and located in the FN by receivingthe mobility agent advertisement and doing mobility detection, and thensends a registration request RRQ to the HA to register the acquiredcare-of address. Here, the FAG is not configured with the AA, therefore,the MN uses the FA1's address as its care-of address. Similarly, whenthe CFA in the VD, i.e., FA1, receives the MN's RRQ, it uses the MN'sHoA as a keyword to look up OVIT, to determine whether there is amatched visitor list entry. In this case, the only difference withrespect to the above example is that the MN uses the FA1's addressinstead of the AA as the care-of address, while the registration processis substantially the same as that in the above example which will not bedescribed any more herein. When the MN's HA intercepts a packet from thecommunication node CN and destined to the HoA of the MN away from theHN, because the FAG in the example is not configured with the AA, the HAforwards the packet completely as specified in IPv4: the packet istunneled to the care-of address indicated in the binding informationmaintained by the HA, Le. FA1. However, assume that MN at this time hasmoved in the VD to the FN2. When FA1 receives the packet, it executesthe abovementioned operations of checking the validity of the tunneledpacket and looking up OVIT by using the MN's HoA as a keyword, and getsknown that the CFA serving the MN currently is FA2 by the shared MNinformation among respective FA members of the FAG, e.g. by OVIT. Thensimilar to the forwarding process mentioned above, FA1 forwards thereceived packet to the MN's CFA, i.e. FA2, which further processes thepacket (if there exists a matched entry, then forwards it to the MN,otherwise discards it). When the roaming MN sends information to a CN,similar to the corresponding processing process mentioned above, CFA,i.e., FA2, determines whether the MN is a registered visitor whenreceiving the data packet. If CFA finds that the MN has alreadyregistered when moving into FN1 according to information maintained byitself or the MN information shared among FA members of the FAG, forexample, by looking up OVIT, then the packet will be forwarded to theCN, otherwise be discarded silently.

As it can be seen from the above examples, even if the FAG is notconfigured with the AA, it still can realize the invention. That is, forthe FAG without AA, when MN uses the address of the FA which is servingit currently as the FACoA, the FA receiving a packet from the HA anddestined to the MN is not the FA within the FAG nearest to the HA anymore, but the FA (FA1 in the above example) which provides registrationwhen the MN moves into the VD for the first time.

2. Using Co-located Care-of Address CoCoA as care-of address

In the case where MN uses the CoCoA as its care-of address, the basicidea is similar to that in the “FACoA” case. In this embodiment. MNstill needs a FA to relay the RRQ and RRP, and also needs a FA tomaintain the visitor list entry for registered MN, so as to accomplishinformation sharing of MN among FA members. Wherein, the MN'sregistration process is similar to the processing process in the FACoAcase. The difference is: VD is the largest scope within which MN cankeep CoCoA as its current care-of address (the visited domain is stillan area which covers the networks served by the FAG); “MN's CoCoA”(wherein “R” bit is set) is also included in the OVIT maintained by FAmembers of the FAG, for storing the CoCoA, and the keyword for lookingup OVIT is the outer IP destination address of the tunneled data packet,i.e. the MN's CoCoA. The detailed description is as follows:

In the registration process, when the MN moves across networks in theVD, it does mobility detection and acquires a CoCoA by for example DHCPor the like. The prior art has specifications specifying how the MNacquires the CoCoA in detail, thus will not explain in this invention.Then, the MN initiates a Registration process to register its newlyacquired CoCoA with the HA as its care-of-address. When a FA in VDreceives the RRQ, it looks up OVIT using the MN's CoCoA as a keyword todetermine whether there is a matched visitor list entry for the MN.Similar to the processing procedure in which MN uses FACoA as itscare-of address, if there is no matched entry, that means the MN entersinto VD for the first time. Then FA needs to register the CoCoA of theMN in the VD with the MN's HA to complete the registration process, andcreate a visitor list entry in both VIT and OVIT maintained by the FA,then distribute the update information to other FA members within thegroup. If there exists a matched entry, that means the MN does not moveinto the VD for the first time, and the FA only updates the entry anddistributes the update information to other members in the FA groupinstead of registering MN's CoCoA with MN's HA.

In the forwarding process, for a packet sent by CN and destined to HoAof MN away from the HN, MN's HA intercepts the packet. HA forwards thepacket as specified in IPv4, preferably in Mobile IPv4: the packet willbe tunneled to the CoCoA indicated in the binding information maintainedby the HA. The tunneled packet will be forwarded directly to the MNaccording to algorithms such as longest matching prefix lookup algorithmor the like.

For a packet from a roaming MN and destined to a communication node, thepacket is forwarded directly to a default router, usually the CFA.Similarly, the CFA checks whether MN is a registered visitor, compareswith the HoA in OVIT using the source IP address of the data packet(i.e. the HoA) as a keyword, to determine whether there is a match. Ifthere is a matched entry, the packet source is a registered visitor andthe CFA forwards the packet to the CN by a normal forwarding mechanism.Otherwise, if there is no matched entry in the CFA's OVIT, the packet isnot from a registered visitor and is discarded silently.

As it can be seen from the above, except the OVIT content and lookupkeyword are different, registration processing flows when MN uses theFACoA and the CoCoA as its care-of address, as well as flows offorwarding packets from the MN to the CN, are similar. For a data packetfrom the MN to the CN: the MN still sends the data packet to a defaultrouter (usually the CFA), and the default router checks the validity ofthe packet and forwards it to the next hop IP node towards to thecorresponding node.

The cases where the MN uses the FACoA and the CoCoA as its care-ofaddress are described above respectively. In the above example, in acase where a FA member only maintains one type of lists, i.e., VIT orOVIT, the above lookup operation is correspondingly changed to look upthe table maintained by the FA itself.

In the above mentioned solutions, FA using MN's HoA, CoCoA as keywordsrespectively to look up VIT/OVIT has been described as examples. Thoseskilled in the art should understand that the selection of the keywordis not limited to the MN's HoA and CoCoA, while any information capableof distinguishing roaming MNs from each other can be used as a keyword.As an example, the operation of updating the MN information when the FAdetermines whether the MN is entering into VD for the first time is alsodescribed above, those skilled in the art should understand thatdepending on the FA's services, the above update operation and theprocessing of the MN's various requests do not have to be performedconcurrently.

Preferably, when the abovementioned discarding operation is performed,only the operation of discarding silently is performed, not performother discarding-related operations. For example, no message destined tothe source address of the discarded message is generated and there is norecord on the log.

According to the solution of the invention, there may be many ways toform the FAG and to distribute OVIT, depending on computing resourcesowned by FA members thereof. The example of composition of the FAG shownin FIG. 3 is based on the assumption that each FA member has roughlyequal computing resources and load capability. In this case, any one FAmember can directly distribute update information of the MN thereon,such as OVIT update, to other FA members of the FAG. However, ifcomputing resources and processing loads are not balanced among FAmembers of the FAG, we can choose a FA member having redundant computingresources as a Forwarding Cooperative FA of the FAG. Optionally, inaddition to performing the same operations as those by intra-group otherFA members, the Forwarding Cooperative FA is further responsible fordistributing the MN information shared within the FAG. Specifically for,whenever any FA member has updated information to send to other FAmembers of the FAG, the FA does not directly send the information toother FA members, but first sends it to the Forwarding Cooperative FA,which decides to send the updated information to which FA members,preferably, to the FAs which need the updated information. For example,when there are many FA members in the FAG, according to whether theupdated information is a newly added entry, i.e. whether the entry isdetermined by the Forwarding Cooperative FA as the one created by the MNwhich enters into VD for the first time, if so, the ForwardingCooperative FA can decide to send it to all the FA members of the FAG;otherwise, the Forwarding Cooperative FA can select FAs which may needthe updated information during next period of time based on thedistances from FA members to the MN's CFA and to the MN's HA.

Optionally, it is also possible to set a separate FA as the ForwardingCooperative FA to mainly accomplish maintenance of the MN informationshared in the FAG. As shown in FIG. 8, VD contains four FAs, whereinFA1-3 have no difference with respect to FAs as shown in FIGS. 3 and 4,and we name this kind of FAs as “Big Cooperative FA”. Functions of FA4in the group are a subset of functions of FA1-3 and are set to be usedfor partaking data forwarding loads. FA4 in FIG. 8 only has thefollowing two parts of functions: OVIT maintain, Data packet forwarding,and we name this kind of FAs as “Forwarding Cooperative FA”. All theother FA members of the FAG, FA1-3 in this example, send OVIT updatesthereon to FA4, which is responsible for maintaining all of the OVITupdates in the FAG and managing the distribution of the OVIT updates toother FA members which need the updated information. In addition, for adata packet from the HA, as shown in FIG. 8, because FA4 is the FAmember nearest to the HA (policy-based), the data packet from the HAwill first arrive at FA4, and FA4 looks up its OVIT to further determinethe MN's CFA and then forwards the data packet to the CFA, which thensends the data packet to the roaming MN. For a data packet from theroaming MN and destined to the CN, the forwarding process is the same asthat in the above embodiment.

Here, we further explain why the Forwarding Cooperative FA can partakedata forwarding loads. In the example shown in FIG. 3, data packets fromdifferent HAs to the AA can arrive at any member of the FAG, whichmember of the FAG it eventually arrive at depending on the locations ofthe HAS in the network topology and the routing policy. Therefore, ifdeploying the Forwarding Cooperative FA at an appropriate networklocation (for example, based on routing topology), a certain number ofdata packets destined to the AA can be absorbed, so as to reduce theforwarding load of some or all of Big Cooperative FAs in the FAG.Preferably, according to statistics, the location deploying theForwarding Cooperative FA can be one of the input points with thelargest data packet throughput of the VD, then most data packetsdestined to the AA will first arrived at the Forwarding Cooperative FAand then be forwarded to the CFA. Another example of deploying thelocation of the Forwarding Cooperative FA is, deploying it at main/hubpaths from many different HAs to FAG members, so as to reduce forwardingloads of FA members of the FAG as much as possible. Therefore, in thisexample, deciding the forwarding loads of which Big Cooperative FAs canor need to be partook is very import for the location selection of theForwarding Cooperative FA.

With the FAG provided by the present invention, through sharing the MNinformation among FA members of the FAG, it is allowed that during themovement of the MN across the VD, only needs the CFA to register theMN's care-of address with HA when the MN enters into VD for the firsttime, instead of performing registering process each time the MN movesfrom one Foreign Network FN within VD to another FN within VD.Therefore, it realizes that the FAG acts as a single FA to the HA andMN, which brings out that the IPv4 based HA and MN can cooperate withthe FAG without any change. That is, according to the solution of theinvention, not only signaling registered by the roaming MN with its homeHA is greatly reduced, thereby network layer handover delay is greatlyreduced, but also the MN and HA in the prior art can benefit from thesolution of the invention.

The method and means of the invention may be implemented by software, byhardware or by a combination thereof, such as computer instructions,means and modules implementing the method of the invention, readablestorage medium storing computer instructions for performing the methodof the present invention, computers including processors, whichprocessors can be used to perform the method of the invention, orsimilar implementation ways easily conceivable by those skilled in theart.

The invention claimed is:
 1. A method for registering with a Home Agentof a Mobile Node in an Internet Protocol Version 4 (IPv4) network, theIPv4 network comprising at least one Mobile Node, a Home Agent, and aplurality of Foreign Agents, the method comprising: selecting at leasttwo Foreign Agents from the plurality of Foreign Agents to form aForeign Agent Group having a coverage area; Foreign Agent members withinthe Foreign Agent Group sharing information of a Mobile Node roaminginto the Foreign Agent Group coverage area, wherein the Foreign Agentsof the Foreign Agent Group maintain a Visitor Information Table tomaintain the Mobile Node's information, wherein the Visitor InformationTable is created by a registration process of the IPv4 network at theForeign Agent members of the Foreign Agent Group, and wherein theVisitor Information Table comprises information about the Mobile Node'shome address, a Home Agent address, an address of a current ForeignAgent, and a lifetime of the current registration, wherein the currentForeign Agent indicates which Foreign Agent is providing services to theMobile Node currently; when at least one Foreign Agent member of theForeign Agent Group receives a registration request to register acare-of address with the Home Agent from a Mobile Node, determiningwhether the Mobile Node enters into the Foreign Agent Group coveragearea for the first time according to the shared MN information; if theMobile Node enters into the Foreign Agent Group coverage area for thefirst time, the Foreign Agent forwarding the received registrationrequest to the HA; otherwise, the Foreign Agent directly sending aregistration response to the Mobile Node.
 2. The method according toclaim 1, wherein the Foreign Agents of the Foreign Agent Group may belink neighboring, subnet neighboring or network coverage areaneighboring Foreign Agents.
 3. The method according to claim 1, whereinwhen the Mobile Node uses a Foreign Agent Care-of Address as the care-ofaddress, the Foreign Agent Care-of Address is an address of the ForeignAgent which is serving the Mobile Node currently, or an Anycast Addressconfigured to the Foreign Agent Group; and that when the Mobile Nodeuses a Co-located Care-of Address as the care-of address, the Co-locatedCare-of Address within the Foreign Agent Group coverage area isconfigured for it.
 4. The method according to claim 1, wherein theForeign Agent determines whether the Mobile Node enters into the ForeignAgent Group coverage area for the first time according to the MobileNode's Home Address or Co-located Care-of Address.
 5. The methodaccording to claim 1, wherein the Foreign Agent updates the Mobile Nodeinformation, and marks itself as the Foreign Agent which is serving theMobile Node currently.
 6. The method according to claim 1, wherein apart of the Foreign Agent members of the Foreign Agent Group is selectedas a Forwarding Cooperative Foreign Agent to be responsible fordistributing and maintaining the shared Mobile Node information, or adedicated Forwarding Cooperative Foreign Agent is set in the ForeignAgent Group for distributing and maintaining the shared Mobile Nodeinformation and forwarding data packets.
 7. The method according toclaim 6, wherein the dedicated Forwarding Cooperative Foreign Agent isset up at a main path from the Home Agent to the Foreign Agent member ofthe Foreign Agent Group.
 8. A Foreign Agent Group for registering with aHome Agent of a Mobile Node in an Internet Protocol Version 4 (IPv4)network, the IPv4 network comprising at least one Mobile Node, a HomeAgent and at least two Foreign Agents, wherein: at least two of saidForeign Agents are adapted to form a Foreign Agent Group, the ForeignAgent members of the Foreign Agent Group being adapted to shareinformation of a Mobile Node roaming into a Foreign Agent Group coveragearea; the Foreign Agents of the Foreign Agent Group are configured for:acquiring shared information from other Foreign Agents of the ForeignAgent Group, wherein the Foreign Agents of the Foreign Agent Groupmaintain a Visitor Information Table to maintain the Mobile Node'sinformation, wherein the Visitor Information Table is created by aregistration process of the IPv4 network at the Foreign Agent members ofthe Foreign Agent Group, and wherein the Visitor Information Tablecomprises information about the Mobile Node's home address, a Home Agentaddress, an address of a current Foreign Agent, and a lifetime of thecurrent registration, wherein the current Foreign Agent indicates whichForeign Agent is providing services to the Mobile Node currently;determining whether a Mobile Node enters into the Foreign Agent Groupcoverage area for the first time according to the shared information,when a registration request for the Mobile Node registering a care-ofaddress with the Home Agent is received; and forwarding the registrationrequest to the Home Agent if there is a determination that the MobileNode enters into the Foreign Agent Group coverage area for the firsttime; otherwise, directly sending a registration response to the MobileNode.
 9. The Foreign Agent Group Foreign Agent Group according to claim8, wherein when the Foreign Agent determines that the Mobile Node doesnot enter into the Foreign Agent Group coverage area for the first time,it marks itself as the Foreign Agent which is serving the Mobile Nodecurrently.
 10. The Foreign Agent Group according to claim 8, wherein theForeign Agent member sets a care-of address in a mobility agentadvertisement extension in an agent advertisement as an Anycast Addressor an address of the Foreign Agent, or configures a Co-located Care-ofAddress within the Foreign Agent Group coverage area for the Mobile Nodeas the care-of address.
 11. The Foreign Agent Group according to claim8, wherein a part of the Foreign Agents of the Foreign Agent Group isset as at least one Forwarding Cooperative Foreign Agent that isresponsible for distributing and maintaining the shared Mobile Nodeinformation, or at least one dedicated Forwarding Cooperative ForeignAgent is set in the Foreign Agent Group for distributing and maintainingthe shared Mobile Node information and forwarding data packets.
 12. AForeign Agent for registering with a Home Agent of a Mobile Node in anInternet Protocol Version 4 (IPv4) network, the IPv4 network comprisingat least one Mobile Node, a Home Agent, and at least two Foreign Agents,said Foreign Agent are configured for: acquiring shared information fromother Foreign Agents of the Foreign Agent Group, wherein the ForeignAgents of the Foreign Agent Group maintain a Visitor Information Tableto maintain the Mobile Node's information, wherein the VisitorInformation Table is created by a registration process of the IPv4network at the Foreign Agent members of the Foreign Agent Group, andwherein the Visitor Information Table comprises information about theMobile Node's home address, a Home Agent address, an address of acurrent Foreign Agent, and a lifetime of the current registration,wherein the current Foreign Agent indicates which Foreign Agent isproviding services to the Mobile Node currently; determining whether aMobile Node enters into the Foreign Agent Group coverage area for thefirst time according to the shared information, when a registrationrequest for the Mobile Node registering a care-of address with the HomeAgent is received; and forwarding the registration request to the HomeAgent if there is a determination that the Mobile Node enters into theForeign Agent Group coverage area for the first time; otherwise,directly sending a registration response to the Mobile Node.
 13. Anon-transitory computer-usable data carrier storing instructions that,when executed by a computer cause the computer to perform a method ofhandling registration with a Home Agent of a Mobile Node in an InternetProtocol Version 4 (IPv4) network, the IPv4 network comprising at leastone Mobile Node, a Home Agent, and at least two Foreign Agents, themethod comprising: grouping at least two Foreign Agents to form aForeign Agent Group; Foreign Agent members of the Foreign Agent Groupsharing information of the Mobile Node roaming into a the Foreign AgentGroup coverage area, wherein the Foreign Agents of the Foreign AgentGroup maintain a Visitor Information Table to maintain the Mobile Node'sinformation, wherein the Visitor Information Table is created by aregistration process of the IPv4 network at the Foreign Agent members ofthe Foreign Agent Group, and wherein the Visitor Information Tablecomprises information about the Mobile Node's home address, a Home Agentaddress, an address of a current Foreign Agent, and a lifetime of thecurrent registration, wherein the current Foreign Agent indicates whichForeign Agent is providing services to the Mobile Node currently; whenat least one Foreign Agent member of the Foreign Agent Group receives aregistration request for registering a care-of address with the HomeAgent sent by a Mobile Node, determining whether the Mobile Node entersinto the Foreign Agent Group coverage area for the first time accordingto the shared Mobile Node information; if the Mobile Node enters intothe Foreign Agent Group coverage area for the first time, the ForeignAgent forwarding the received registration request to the Home Agent;otherwise, the Foreign Agent directly sending a registration response tothe Mobile Node.